The invention relates to a turbine engine blade preform, such as in particular a turbine blade preform in a turbine engine, and a mold and a method for obtaining the blade preform.
In the current technique, the turbine blades are one-piece parts obtained by molding, using a mold comprising a cavity, the three-dimensional shape of which makes it possible to obtain the desired shape in a form-fitting manner. In practice, the part obtained after the step of molding consists of a blade preform which has to be machined to reach the desired final shape and dimensions.
Thus, a turbine blade preform comprises a strut connecting a blade root to a plat-form. The blade preform also has two transverse upstream and downstream webs formed at the upstream and downstream ends of the strut and connecting the upstream and downstream edges of the plat-form to the upstream and downstream ends of the blade root, respectively. It should be noted that the terms “upstream” and “downstream” are to be considered relative to a general upstream to downstream fluid flowing direction around the blade when the latter is mounted in a turbine engine.
When viewed in an upstream/downstream direction, each web of the blade comprises side edges connected to the blade root flanks through concave curved walls which extend towards each other and form a throat area the width of which measured in a transverse direction is smaller than that of the blade root.
The presence of a throat at the junction between each web and the blade root makes it possible to limit the time required for the final machining of the blade root. To obtain such above-mentioned throats, the mold must also comprise the matching throat areas.
However, when the liquid material flows into the mold, the mold throat areas slow down the flow of material at these locations, which may lead to interrupted solidification and cold lap which may lead to a poor solidification of the material and the forming of mechanical defects, such as cracks in the connecting areas of the side webs to the preform of the blade root.